Edward R. Murrow's audio essays with the famous -- and not-so-famous -- have been digitized and put online

They represent a slice of American cultural history, says project engineer from Iron Mountain

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DiLeo said the Murrow tapes were challenging to restore not only because of their worn condition but also because they contained no "test tones," which help recording engineers align audio to digital recorders to the proper audio levels.

Instead, the engineers used calibration tapes from Magnetic Reference Laboratory (MRL) to set their machines to the proper audio inputs.

The engineers captured the analogue recordings using a 96K, 24-bit high resolution WAV format. By recording the audio in its raw state, the engineers were able to keep a gold copy of it.

Tech monitors playback
Sometimes, cleaning the magnetic tape is not enough, so a process called baking removes water that has accumulated in the binder to allow for stabilized playback. The tape is placed in an electric oven, and then the temperature is slowly increased to 130 degrees Fahrenheit, then cooled back to room temperature. Then, the playback is captured to a high-resolution (24bit/96kHz or higher) digital broadcast wav file (.wav) for preservation.

The engineers then listened to each recording, picking out hissing, scratches or any other background noises for later deletion. The audio was then fed through servers with proprietary software that found the optimum noise reduction for removing any "sonic artifacts." After that, minor equalization changes were made to give the vocals additional clarity.

Grant Fletcher, an Iron Mountain studio engineer who worked on the Murrow restoration project, said it was a slice of cultural American history.

"A slice that cannot be examined or duplicated today in any way -- a pure, honest, undiluted view of the people," Fletcher said. "It was a glimpse into the hearts and minds of citizens, the wealthy, the blue collar, the recent immigrant, the American whose family had been here since the founding of this country."

This article, Edward R. Murrows audio essays with the famous -- and not-so-famous -- have been digitized and put online, was originally published at Computerworld.com.

Lucas Mearian covers storage, disaster recovery and business continuity, financial services infrastructure and health care IT for Computerworld. Follow Lucas on Twitter at  @lucasmearian or subscribe to Lucas's RSS feed . His e-mail address is lmearian@computerworld.com.

See more by Lucas Mearian on Computerworld.com.

Copyright © 2013 IDG Communications, Inc.

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